The U.N. refugee agency reports more than 3.5 million refugee children aged five to 17 did not attend school last year to the detriment of their future and the future well-being of society. The UNHCR is calling an education crisis for refugee children.

Children make up half of the 17.2 million refugees around the world and many of them are missing out on a productive future because they do not go to school.

Children of Rohingya refugees attend a temporary school run by a non-governmental organization at a camp for Rohingyas in New Delhi, India, Aug. 16, 2017.

The UNHCR warns neglecting the education of millions of refugee children will undermine the U.N.’s Sustainable Development Goals — principally those targeting health, prosperity, equality and peace.

The refugee agency reports 91 percent of the world’s children attend primary school, compared to 61 percent for refugee children. It says that number drops to below 50 percent for refugee children in poor countries.

The agency finds those numbers drop precipitously as refugee children age, especially in the poorer countries. It says far fewer adolescents attend secondary school and enrollment in university is stuck at one percent.

“There is a clear need for more solidarity and for making sure that people who take refugees in low income countries also have access to education. This is crucial," she said. "We know that these refugee children will one day go back to their home places and rebuild their countries. So, they are the future. If we do not invest in their future, we do not invest in the world’s future.”

FILE - Syrian refugees pose for a photo during a visit by U.N. Secretary General Antonio Guterres to a fourth-grade classroom at the U.N.-run Zaatari camp for Syrian refugees, in northern Jordan, March 28, 2017.

The UNHCR urges governments to include refugee children in their national education systems.

It also calls for more efforts to ensure refugee children are taught by properly trained and qualified teachers.